Turning Concrete Into an Eco-Friendly Material

From roads to skyscrapers, concrete seems to be omnipresent, which is why making it more environmentally friendly could provoke a considerable impact on the world. But how can this be achieved in the short term?

The use of waste materials from different industries has been increasing and architecture and construction are leading the trend, supported by scientists and engineers experimenting with new green solutions.

Turning waste into new materials, or "upcycling", means an important carbon-print reduction for a given industry. Upcycling agricultural or industrial waste that might otherwise pollute the environment could be an answer to the planet's increasing waste production rate.

Following are some ways in which concrete can be turned into an eco-friendly material, not only changing its composition to make it greener but by including waste and byproducts as additives into its composition, thus giving it new exciting properties.

Fly Ash and Bottom Ash

Zeitz MOCAA by Heatherwick Studio

Fly ash and bottom ash are highly pollutant waste compounds derived from a wide variety of coal-burning industries. Repurposing this form of waste keeps the environment clean from air pollutants and retains the soil's integrity as some industries collect the fly ash before it can go airborne and end up in landfills, where it can then infiltrate water resources and poison the land. By collecting fly ash directly from the chimneys and bottom ash from the furnace, and then mixing them with Portland cement, this highly pollutant residue becomes a valuable resource instead.

According to recent studies, when natural sand is replaced by fly ash, concrete's workability increases considerably.

Corn Cob Ashes

Concrete House by BAK Arquitectos

Corn cobs can be turned into an eco-friendly pozzolan by transforming the material into ash. The cobs are ground into a coarse powder, then slowly incinerated at high temperatures (680°F) for eight hours. The resulting ashes’ chemical composition consists mainly of Silicone monoxide (SiO, 66.38%) and aluminum oxide (Al2O3 7.48%). Compounds found in clinker are used to make regular Portland cement but in a higher percentage, which makes corn cob ash more suitable for the task as their percentages combined exceed the norm of a 70% percent minimum. Corn cob ash particles are finer than that found in clinker, making a corn cob ash blend smoother than a regular clinker mix.

Oil Palm Shells

Box House by WHBC Architects

With a rise in coconut oil consumption in cosmetics and food industries, so rises the waste produced by leftover palm shells resulting from oil extraction. Malaysia, the world's biggest producer, extracts up to seven million tons of coconut oil a year––resulting in consequential waste.

Oil palm shells are 60% lighter than most coarse concrete aggregates, making the material a suitable candidate for creating lightweight and sturdy concrete mixes. In addition, the shells possess a low Los Angeles abrasion value––80% lower than traditional aggregates––meaning they have a high resistance to crushing and disintegration. The older the oil palm shells the better, as the lack of fiber around them allows the shells to bond better with the cement.

While this product hasn’t been tested for time durability yet, it shows promise and could be a suitable answer for coconut oil producing countries.

Rice Husk Ashes

Cidade Das Artes by Christian de Portzamparc

Rice is one of the most consumed grains in the world. When making white rice, tons of husks are discarded in the process. This method repurposes these leftover husks by mixing them into the concrete, giving the material a new life instead of letting it go to waste. The ashes are incinerated at 1472°F and the resulting particles are finer than regular pozzolan. Their honeycomb molecular structure allows them to sit evenly into the mix, providing structural stability.

According to studies, the resulting mix has a high compression strength, antifreeze properties––relevant in cold climates––and a good resistance to chloride ion penetration––which increases its durability when compared to regular Portland cement mixtures.

Steel Slag

Steel Slag, a byproduct of the steel industry, can be turned into a concrete aggregate as well. By replacing natural sand––ideally, at a maximum of 50% to avoid a decrease in workability––this mixture possesses a high density, which translates into a strength increase in the final product.

By mixing steel slang into the concrete, water absorption decreases, which means this material behaves well in freezing temperatures, thus increasing its durability.